em

Any update on this? Or at least another way to calibrate homing back off. I really just need a way to align my homing switch back off with the fixtures on my table. I could do this if I could align it to 0,0 manually using precise measuring, and then get the machine to “measure to homing switch”, the result of which I can make the back offs.

I was really hoping I could get this from the filtered position feedback but unfortunately the position data is always missing that one last exact position before it gets set to 0.

I tested this by doing
G0 X10
G28.3 X0
G28.2 X0

And every time I get something like this:
posx:-14.123
posx:-12.083,vel:494.375
posx:-10.426,vel:266.389
posx:-9.981,vel:11.736
posx:0.000,vel:0.000,coor:1,dist:0,stat:3

Really was hoping 10 would be in there, but it seems to be reporting pos after that set to 0 happens. : [

I think what I’m gonna have to do to workaround this, is home first, rapid to something close to what my 0,0, and then come up use some kind of material jig that allows me to precisely measure the remaining difference to true 0 with a micrometer. Since my table is a grid of bolt holes, I can put a bolt in one hole securely, and do some arithmetic given the bolt diameter measured with a micrometer, and the distance between a precise rod in the spindle to the outer edge of the bolt, also with a micrometer.

For people in the future it would be easier for them to be able to manually touch a precise rod in the spindle against an edge and then find the distance to home. It would also minimize the cumulative error by introducing the micrometer’s inaccuracy into the equation.

• This reply was modified 10 years, 7 months ago by em.